WASHINGTON (CNN) -- The Transportation Security Administration announced late Wednesday that it is modifying pat-down procedures at airports -- a decision that comes after hundreds of complaints, most of them from women, that the procedure is too intrusive.

Under the new guidelines, screeners will not be able to pat-down a passenger's breast area unless the handheld metal detector goes off or if there is an irregularity in the passenger's clothing outline, said TSA spokesman Dave Steigman.

Steigman said that under the new policy, passengers will have their sides patted down. Once that is done, there will be a limited torso pat-down from front to back, from a line below the chest area to the waist. Screeners will pat the entire back.

He also said people in wheelchairs will not have to get out of their wheelchairs for the pat-downs. The screening will be done while they are seated, using the wand and explosive trace detection machines, he said.

However, he said other passengers who cannot walk through the metal detector, including people with walkers, will have to undergo the full body pat-down.

The new procedures take effect Thursday, Steigman said.

He would not say what prompted the change. He said criticism to the agency of the pat-downs has amounted to a few hundred complaints out of an estimated 50 million passengers who have flown since the procedure was implemented.

The TSA began conducting the full body pat-downs in August after female suicide bombers downed two Russian airliners, killing 89 people.

Many of the complaints about the pat-downs have come from women who said they felt violated by them.

Helen Chenoweth-Hage, a former Republican congresswoman from Idaho, said screeners at the Boise airport refused to reveal the regulations allowing them to pat her down -- angering her so much she drove the more than 300 miles from Boise to Reno, Nevada.

"I was absolutely astounded at the fact that they thought they could violate my Fourth Amendment rights, violate my privacy, violate my body because of some secret law," she said.